Encentrum pugiodigitatum, De Smet, Willem H., 2015

De Smet, Willem H., 2015, Rotifera from the Mediterranean Sea, with description of ten new species, Zootaxa 4028 (2), pp. 151-196 : 166-168

Encentrum pugiodigitatum sp. nov.

( Figs 10 , 11 )

Diagnosis. Female about 165−175 µm long. Integument fairly stiff with faint longitudinal folds; toes daggershaped; rami outline elliptical, median rami opening lenticular; long slender unci with very short tooth; unci with bundle of needle-shaped elements; head of manubria with proximal opening, and associated crenate platelet.

Type locality. Punta della Madonna, Elba Island, Tyrrhenian Sea, Italy. In psammon collected on 25.09.2006, 50 m from shoreline and depth of 30 m; water temperature 21 °C.

Holotype. A female in a permanent, glycerine glass slide mount deposited in the Royal Belgian Institute of Natural Sciences ( RBINS), Brussels, Belgium, No. IG 33082, RIR 220.

Paratypes. One female from type locality in RBINS, No. IG 33082, RIR 250; 5 mounted paratypes and 5 SEM trophi preparations in Department of Biology, University of Antwerp.

Additional material. Several specimens from sublittoral of the Costa Blanca, Balearic Sea, the Côte d’Azur, and Elba Island, Tyrrhenian Sea (see Tab. 2 species list).

Etymology. The name of the species is composed of the Latin pugio meaning dagger, and the Latin digitatum, meaning provided with toes (digitus: toe), and refers to the characteristic shape of the toes.

Description of female. Body stout fusiform ( Fig. 10 ). Integument fairly stiff with faint longitudinal folds. Head offset by neckfold, with weak transversal fold in distal half. Rostrum broad, shallow, straight to broadly rounded. Corona frontal. Dorsal antenna near posterior 1/3 of head. Trunk with some very weak incomplete transversal folds. Tail large, rounded, partly covering foot. Foot large, conical, 2(3) pseudosegments. Toes ( Figs 10 C, D) c. 1/7 total length, dagger-shaped, almost straight in dorsal and lateral view, margins weakly undulate, terminating in more or less distinctly offset claw. Eyespots not observed, possibly absent. Brain large, saccate; retrocerebral sac present. Gastric glands more or less spherical, stalks short to medium length. Proventriculus small. Pedal glands club-shaped, foot-length. Vitellarium with 8 nuclei.

Trophi ( Figs 10 E, 11) with elliptical rami outline, greatest width in distal half; outer rami margins very weakly indented near proximal 1/3; median rami opening almost lenticular; rami elongate, narrow, widest in proximal half, terminating in very short, weakly offset oblique apical tooth; basifenestrae fairly small, elongate, subbasifenestrae fairly large, rounded. Preuncinal teeth very short, apical, in line with apical rami teeth. Fulcrum short, c. 1/3 ramus length, plank-shaped, in lateral view very slightly narrowing towards rounded distal end. Unci long, c. 2/3 ramus length, slender, head very short, weakly offset, bifid, shaft with long dorsal rib. Associated with the unci and running parallel to them are a bundle of about 10 weakly sclerified needle-shaped elements (only shown in Fig. 11 B: ns) provided with a seam; they insert somewhere near the intramallei. Intramallei small, elongate triangular, with caudal opening. Supramanubria small, elongate triangular, with caudal opening. Manubria rod-shaped, evenly curved in dorsal view, distal half with weak dorsal torsion in oblique view, slightly crutched distally with small opening and ventral more or less hook-shaped blunt process (only visible by SEM); head simple, distinct dorsal and ventral expansions lacking, with large proximal opening; a small elongate platelet with irregularly crenate margins dorsally from proximal end of manubria ( Fig. 11 B: cp).

Measurements. Body (N=10): total length 165‒175 µm, toe 19‒27 µm; trophi (N=5): length 29 µm, ramus 13.1‒13.4 µm, fulcrum 4.1‒4.5 µm, uncus 9.0‒10.0 µm, intramalleus 1.5‒1.7 × 2.4‒3.1 µm, manubrium 19.0‒19.6 µm.

Comments. Encentrum pugiodigitatum sp. nov. can not be confused with any of its congeners, and is neither related to any of the subgenera erected previously on base of the morphology of the trophi ( De Smet 1997). Proximally open manubria, the crenate platelet associated with the head of the manubria, and the bundles of weakly sclerified elements paralleling the unci have not been reported before.

Distribution and ecology. The species was usually found in low numbers in sublittoral psammon samples from the Costa Blanca, Côte d’Azur, and Tyrrhenian Sea, at distances of 50 m to 3.5 km from the shoreline, and depths between 15 and 40 m. It was present in samples taken in June, August and September, at water temperatures of 17−25 °C.

Figures

FIGURE 10. Encentrum pugiodigitatum sp. nov. A. Female, dorsal; B. female, lateral; C. toe, lateral; D. toe, dorsal; E. trophi, dorsal. Scale bars: A, B: 50 µm; C − E: 10 µm.

FIGURE 11. Encentrum pugiodigitatum sp. nov., SEM photographs of trophi. A. Complete set, dorsal; B. detail, dorsal; C. detail, ventral; D. complete set, ventro-lateral. cp: crenate platelet; ns: needle-shaped sclerite bodies. Scale bars: 10 µm.